c++/1482: va_start generates call to memcpy

[Franz Sirl]

The following reply was made to PR c++/1482; it has been noted by GNATS.

From: Franz Sirl <Franz.Sirl-kernel@lauterbach.com>
To: andyj@mc.com
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c++/1482: va_start generates call to memcpy
Date: Thu, 21 Dec 2000 20:30:28 +0100

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 At 23:07 2000-12-20, andyj@mc.com wrote:
 
 > >Number:         1482
 > >Category:       c++
 > >Synopsis:       va_start generates call to memcpy
 > >Confidential:   no
 > >Severity:       serious
 > >Priority:       high
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          sw-bug
 > >Submitter-Id:   net
 > >Arrival-Date:   Wed Dec 20 14:16:00 PST 2000
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     E. Andrew Johnson
 > >Release:        g++-2.95.2
 > >Organization:
 > >Environment:
 >target=powerpc with Altivec 2.95.2 patches
 > >Description:
 >The expansion of va_start includes a call to _builtin_memcpy.  When 
 >compiling with the gcc-2.95.2 C compiler, this generates the inline 
 >expansion of the code.  When compiling with the gcc-2.95.2 C++ compiler, 
 >it generates an external call to memcpy.  The problem is that the 
 >type.align for "va_list ap" is set to 1, whereas it is
 >set to 8 (1 byte) in C.  Why does it behave differently
 >with the C++ compiler?
 
 Nobody knows :-). This was fixed a few days after gcc-2.95 came out, Bernd 
 Schmidt and others commonized the tree node handling with C/C++ and thus 
 fixed the bug. For gcc-2.95.2 you can try the appended patch which copies 
 the void_type_node TYPE_ALIGN handling from c-decl.c to cp/decl.c.
 
 Franz.
 
          * decl.c (init_decl_processing): Align void_type_node to 
 BITS_PER_UNIT as in C.
 
 
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